Advances in technology fostered through the Human Genome Program have made global comparative assessment of differences between genomes and their gene expression a reality. Funds are being requested for the purchase of the Affymetrix 437 arrayer in order to upgrade from our Affymetrix 417 arrayer. The 437 will provide several advantages over the prototype arrayer currently in use in the DNA Microarray and Genomics Resource, and will allow continued integration with our Affymetrix GeneChip reader, and Affymetrix 428 scanner. The demand for array fabrication has increased dramatically over the past year, and with the current arrayer we are facing a backlog. At present the Affymetrix oligonucleotide arrays are being used in a discovery mode to identify patterns of gene expression in certain cell types and tissues as well as to make highly quantitative comparisons in gene expression levels between paired samples. The new arrayer would provide greater through-put, efficiency, and speed to meet the rising demand from researchers to design their own custom arrays either using genes from our resource clone collection databases, or from a combination of these and GeneChip predictions. Researchers at RPCI and the School of Medicine and Biomedical Sciences at SUNY Buffalo are in a unique position, in that close collaboration with clinical personnel allows access to a wide variety of patient material and identification of many interesting and clinically relevant diseases and syndromes. The ability to define gene function/pathways in model systems as well as define molecular signatures for disease through differential genomic and gene expression analysis will greatly enhance ongoing research programs. The requested instrumentation will afford the DNA Microarray and Genomics Resource with the capacity to continue to provide high quality custom genomic and expression arrays.